Science Experiments for Kids: Air

by saw pan

Science can be a really fun subject for kids, especially when it involves experiments.

A few exciting science experiments not only keep kids entertained, but they also help teach kids about important scientific concepts. In this article, I’ll detail a few exciting experiments that are easy, inexpensive, a lot of fun, and teach your child all about the wonders of air and air pressure.

1. Submarine Sock:

Step One: Take a sock and stuff it into a glass or clear cup. Make sure that the sock is stuffed tightly enough into the glass that it does not fall out when the glass is turned upside down. Step Two: Fill a sink or bowl with water. Step Three: Turn the glass upside down and immerse it in the water. You will notice that even though the glass is completely covered by water, the sock stays dry!

Why does it work? This science trick uses the same air principle as the diving bell did for early ocean explorers. The tiny air particles (invisible to the eye) fill all of the available space in the glass and around the sock. When the glass is immersed upside down in the water, the air particles press against the water and keep it out of the glass (and away from the sock). It is only when you immerse the glass much deeper that the air particles compress, allowing a bit of water into the glass.

2. Floating Water:

Step One: Fill a glass with water, allowing the glass to get so full that the water overflows. A smaller glass works best for this experiment. Step Two: Place a postcard on the brim of the glass. Step Three: Holding the postcard in place, turn the glass upside down. Now, slowly move your hand away from the postcard and be amazed as the water stays in the glass!

Why does it work? Water presses down on the postcard with a pressure of a few ounces per square inch. Air pressure, on the other hand, is pressing upwards on the postcard with a much greater pressure, roughly 100 times as strong. Because the air pressure per square inch (also known as PSI) is greater than the water pressure, the water is able to hang in the glass with only a thin postcard keeping it in the container.

3. The Impossible Postcard:

Step One: Bend a postcard into a curve so that it looks like an arch when placed on a flat surface. Step Two: Place the arched postcard on a table and blow hard underneath it; it will not move! Now try blowing softly underneath the postcard. What happens?

Why does it work? This trick works because of a scientific principle discovered by Daniel Bernoulli – the pressure of gas is higher as it moves at a lower speed. Conversely, gas pressure is lower at a higher speed.

So, the harder you blow on the postcard, the faster the gas (air) is moving, and the lower the gas (air) pressure is underneath the postcard. At this point, the low gas pressure produced by blowing under the card is no match for the more powerful air pressure pressing on the top of the postcard, and the postcard stays in place. The harder you blow the postcard, the more it will cling to the table.

4. Sneaky Air:

Step One: Place a lighted candle on the table. If your little scientist is young, you’ll want to have adult in charge do this step. Step Two: Place a bottle in front of the burning candle; about 6″ (15 cm) is a pretty good distance, but try experimenting with different distances, and see if the results are the same. Step Three: Get in front of the bottle (so that it is directly between you and the candle) and blow. It should look like you are magically blowing out the candle right through the bottle!

Why does it work? When the air flow hits the bottle, the air currents divide and go around the bottle, clinging to the sides of the bottle as they move. The air currents the rejoin on the other side of the bottle and hit the flame of the candle, blowing it out. Since air currents can separate and rejoin without much loss of strength, the air flow will practically be as strong when it hits the candle flame as it was when it originally left your mouth.

5. Speedy Coin Flip:

Step One: Place a coin on the table – a dime works best. Step Two: Lean down so that you are fairly level with the coin and blow on it from the front. Try to blow sharply under the coin. Does it move? Step Three: Now, sharply blow a few inches directly above the coin (blowing straight ahead over the dime) and watch it flip!

Why does it work? When you blow sharply across the top of the coin, the air pressure over the coin is reduced, and the air pressure surrounding the coin flows in several directions. This lifts the coin and allows it to flip across the table. Much like the postcard science trick, the air is not able to lift the coin from underneath; the air currents around the coin must be agitated to eventually lift the coin.